A fascinating biological phenomenon in which cells grow and divide despite a context and history that should prevent proliferation is the regeneration of damaged tissues. Various organisms and tissues are capable of regenerating, and some tissues such as frog limbs and fruit fly larvae lose their ability to regenerate over time. Therefore, these organisms contain genes that can overcome a cell's normal program and induce cell division, and genes that can prevent this cell cycle progression. The work proposed here is designed to identify genes that regulate regenerative growth. First, an assay system will be developed through which regeneration in Drosophila may be studied genetically. Second, genetic screens will be conducted to isolate mutations that affect regenerative growth after tissue ablation. Third, the genes and proteins that control this process will be identified and characterized. Genes that regulate regenerative growth may also regulate the progression of cancers. The identification of genes that specifically regulate cell division during regeneration and cancer progression may provide unique therapeutic targets.